2.3 Class C and Class D Airspace

Class C and Class D Airspace

Class C and Class D wrap airports that are busy but below the traffic levels that justify Class B. Distinguishing them by chart color, shape, and the tower-hours rule is a frequent exam task.

Class C Airspace

Class C ("Charlie") surrounds airports with an operational control tower, radar approach control, and a qualifying volume of IFR operations or passenger boardings.

Dimensions (standard model):

• Inner core (surface area): surface up to about 4,000 ft AGL, extending 5 NM from the airport.
• Outer shelf: from roughly 1,200 ft AGL up to 4,000 ft AGL, extending 10 NM from the airport.
• Outer area: an uncharted 20 NM zone where radar service is available on request but no charted boundary exists.

Chart depiction: solid magenta lines with altitude labels in hundreds of feet MSL; SFC under the inner core marks the surface floor.

Part 107: prior ATC authorization required (LAANC or DroneZone), within all stated conditions.

Class D Airspace

Class D ("Delta") surrounds airports that have an operational control tower but do not meet Class B or C criteria.

Dimensions:

• Surface up to about 2,500 ft AGL (tailored locally).
• Roughly a 4 NM radius, usually a simple cylinder.
• Irregular cutouts exist where airspace is carved out for nearby airports.

Chart depiction: dashed blue lines; the ceiling appears inside a blue boxed number in hundreds of feet MSL — [25] means a 2,500 ft MSL ceiling.

Part 107: prior ATC authorization required (LAANC or DroneZone).

Side-by-Side Comparison

Satellite Airports Inside Larger Airspace

Smaller airports often sit beneath a Class B, C, or D shelf. When operating near one:

• Check both the satellite airport and the overlying controlled airspace.
• You may need authorization keyed to the primary airport's ATC even when working next to the small field.
• The UAS Facility Map already accounts for both, so trust the grid altitude for the cell you are in.

The Tower-Hours Rule (Heavily Tested)

Class D exists only while the control tower is in operation. When the tower closes for the night:

• The airspace may revert to Class E surface area (if a Class E surface designation exists) — and you still need authorization.
• Or it may revert to Class G — and no authorization is needed.
• Tower operating hours are published in the Chart Supplement (formerly the Airport/Facility Directory).

Worked scenario: You plan a 9 p.m. shoot just inside a Class D boundary. The Chart Supplement shows the tower closes at 8 p.m. and the field has a Class E surface area at night. Result: the airspace is now Class E surface area, so you still need authorization. If no Class E surface area existed, it would be Class G and you could fly without one.

Common Traps

• Reversing the colors: solid magenta = Class C, dashed blue = Class D. Mixing these is the single most common chart error.
• Assuming a closed tower automatically means free airspace — it may become Class E surface area, which still requires authorization.

A Color Mnemonic That Survives Test Stress

The color scheme trips up more candidates than any other chart fact, so lock it with a pattern rather than rote memory. Class B and C are drawn solid because their boundaries are firm and continuously active; Class D and Class E surface areas are dashed because they can change state (Class D follows tower hours, Class E surface areas exist around airports without a tower). Then pair the colors: blue rides with the towered, higher-tier airspace (B solid blue, D dashed blue), while magenta rides with the radar core and the non-tower surface area (C solid magenta, E surface dashed magenta).

If you can reconstruct that grid, you can answer any color question without guessing.

How the Two-Way-Radio Rule Differs for Drones

Manned pilots must establish two-way radio communication before entering Class C or D, and the exam may quote this to imply a drone must do the same. It does not. A Part 107 drone has no radio requirement; the authorization obtained through LAANC or DroneZone is what satisfies the access requirement. The distinction matters because chart questions sometimes embed manned-aircraft entry rules as plausible-sounding wrong answers. The only thing a Part 107 pilot needs to enter Class C or D is a valid airspace authorization plus compliance with all standard operating rules.

Worked Scenario

You want to film a high-school stadium that sits 3 NM from a Class D field. The Chart Supplement shows the tower operates 0700-2100 local, and a Class E surface area is designated when the tower is closed. For a 2 p.m. shoot the field is Class D: get a LAANC or DroneZone authorization. For a 10 p.m. shoot the tower is closed and the field becomes a Class E surface area (dashed magenta): you still need authorization. Only if no Class E surface area were designated would the after-hours airspace drop to Class G and free you from an authorization.

Always read the Chart Supplement hours before assuming the airspace class for your planned time.